This article, which takes a fresh look at micro–macro relations in the social sciences from the point of view of the mechanistic account of explanation, introduces the distinction between causal and constitutive explanation. It then discusses the intentional fundamentalism, and challenges the idea that intentional explanations have a privileged position in the social sciences. A mechanism-based explanation describes the causal process selectively. The properties of social networks serve both as the explananda and the explanantia in sociology. Knowledge of the causal mechanisms is vital in the justification of historical causal claims. The intentional attitudes of individuals are also important in most mechanism-based explanations of social phenomena. It is important to pay closer attention to how real macro social facts figure in social scientific theories and explanations.